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From what I know humic acids are not really soluble in normal water, so to have a liquid form you need high pH (9 seems common). I looked into lignohumate and this is the definition I found: Lignohumate is an industrially produced analog of natural humic substances, produced by thermal processing of technical lignosulfonate (so by processing some byproduct of wood industry).

As biscuitridge said, it's mostly about micronutrients (they benefit the most from chelating). If you don't feel you are limited by their availabilty, humates won't really help (also, unless you are using pure hydroponic setup, you will have some humates in there). The cheaper source of these would be manure (some more than others, I think cow is quite good), old decomposed peat, compost.